{"id":"BIT-oauth2-proxy-2026-76835","summary":"OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set","details":"OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for CVE-2026-40575 is inert in the default reverse-proxy configuration. GetRequestURI in pkg/requests/util/util.go prefers that header over the real request URI whenever CanTrustForwardedHeaders returns true, and isAllowedPath in oauthproxy.go matches the skip_auth_routes and skip_auth_regex allow list against the resulting path. CanTrustForwardedHeaders in pkg/apis/middleware/scope.go grants that trust when the caller's address is in the trusted proxy set, and buildTrustedProxyNetSet falls back to defaultTrustedProxyIPs, which is 0.0.0.0/0 and ::/0, whenever reverse proxy mode is enabled without trusted_proxy_ip configured. Every client is therefore treated as a trusted proxy. An unauthenticated attacker can request a protected upstream path while setting X-Forwarded-Uri to a value matching an allow-listed route, so the skip-auth decision is made against the spoofed value while the upstream receives the protected path unchanged.","aliases":["BIT-oauth2-proxy-2026-40575","CVE-2026-40575","CVE-2026-76835","GHSA-7x63-xv5r-3p2x","GO-2026-5236"],"modified":"2026-09-25T14:25:56.584542414Z","published":"2026-09-25T12:27:39.116Z","database_specific":{"cpes":["cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:go:*:*"],"severity":"Critical"},"references":[{"type":"WEB","url":"https://github.com/oauth2-proxy/oauth2-proxy"},{"type":"WEB","url":"https://github.com/oauth2-proxy/oauth2-proxy/blob/v7.15.4/pkg/apis/middleware/scope.go"},{"type":"WEB","url":"https://github.com/oauth2-proxy/oauth2-proxy/issues/3506"},{"type":"WEB","url":"https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76835"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/oauth2-proxy-through-authentication-bypass-via-x-forwarded-uri-under-the-default-trusted-proxy-set"}],"affected":[{"package":{"name":"oauth2-proxy","ecosystem":"Bitnami","purl":"pkg:bitnami/oauth2-proxy"},"ranges":[{"type":"SEMVER","events":[{"introduced":"7.15.2"},{"last_affected":"7.15.4"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/oauth2-proxy/BIT-oauth2-proxy-2026-76835.json"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"}]}],"schema_version":"1.9.0"}